The Book of Psalms has a certain grace of its own.

For in addition to the other things in which it enjoys fellowship with the other books of the Bible, it possesses this marvel – that it contains all the emotions of each soul and their various changes.

Thus, through hear­ing, it teaches us not only not to disregard passion, but also how to heal passion through speaking and acting.

There is also this astonishing thing in the Psalms. After the prophecies about the Saviour and the nations, he who recites the Psalms is uttering the rest as his own words, and each sings them as if they were written concerning him.

And it seems to me that these words become like a mirror to the person singing them, so that he might per­ceive himself and the emotions of his soul.

For in fact he who hears the cantor receives the song that is recited as being about him, and either, when he is convicted by his conscience, he will repent, or hearing of the hope that resides in God, and how this kind of grace exists for him, he exults and begins to give thanks to God.

Therefore, when someone sings the third psalm, recognising his own tribulations, he considers the words in the psalm to be his own.

And then when someone sings the fiftieth, he is speaking the proper words of his own repentance.

If the point needs to be put more forcefully, let us say that the entire Holy Scripture is a teacher of virtue and the truths of faith, while the Book of Psalms presents the perfect image for the soul’s course of life.

[…] Just as the harmony that unites flutes effects a single sound, so also, seeing that different movements appear in the soul, reason intends man to be neither discordant in himself, nor to be at variance with himself.

Reason intends the soul possessing the mind of Christ to use this as a leader, and by it to be a master of its passions.

A man then becomes a stringed instrument and, devoting himself completely to the Spirit, obeys the mind of Christ, which acts like a plectrum in all his members and emotions, thus enabling him to serve the will of God.

The harmonious singing of the Psalms is a figure and type of such order and tranquillity.

For just as we discover the ideas of the soul and communicate them through the words we put forth, so also the Lord, wishing the melody of the words to be a symbol of the spiritual harmony in a soul, has ordered that the odes be chanted tunefully, and the Psalms recited with song.

Athanasius of Alexandria (c.293-373): Letter to Marcellinus 10-12, 14, 27-29; from the Monastic Office of Vigils, Tuesday of the Twenty-First Week of Ordinary Time, Year I.